Im just about to pull the trigger on a ST-E3-RT and 600EX-RT that iv been having a play with.. I tried very quickly to see if it was possible to trigger two 580exii while in slave mode and the 600EX-RT in slave while using the ST-E3-RT to fire the 600, I unfortunately couldnt get the 580's to fire... But if I put the 600 on camera it fired the two 580's with no problem.. Im not after full ETTL, more than happy just using it fully manual...

If anyone can shed a bit light on this subject it would be much appreciated..Regards Alex

Just like Highlander (with apologies for the bad movie reference), "There can be only one." There's one master, everything else is a slave. If the 600 is a slave (ST-E3 as master), it can't trigger a 580.

But, you mentioned not needing automatic metering. In that case, why not just a set of 'dumb' RF triggers? Yongnuo, Cactus, etc., would all work.

It would...if you replaced your 580s with 600s (and I'm sure that's what Canon wants you to do). I expect that there will be a 430-replacement that's an -RT version (likely slave only). Then, at some point in the future (likely when 600 and 4xx -RT sales wane), Canon will release an -RT receiver-only with a hotshoe for older flashes. Yongnuo may beat them to the latter.

They did make a hybrid - it's called the 600 EX RT Don't forget, you can trigger from the 600 to a mix of 430, 580 and 600 flashes using optical, and if you need you can go Menu1, then left soft menu option (toggle flash) to disable the flash onboard the master. This is how I normally shoot with 2 x 600's and 1 x 430. In NZ the ST-E3-RT is nearly as expensive as the 600, so it wasn't hard to decide to go for the full unit.

As always, great forum. Everything that has been mentioned about 580EXII being optical only, STE3 being radio only, and the 600 being both radio/optical is correct. I would only add to this, there can be more than 1 Master. We tried this, this past weekend at a wedding ceremony, at the beach and at night, so it was a real nightmare as far as lighting goes. We clamped 2 600s on the sides of the huppah (1 on each side) and acting a slaves. My wife was covering the ceremony with 2 5D3s, one with a 24-70 and the other with a 70-200, each camera with a 600 acting as master.

This worked flawlessly, she would switch from one camera to the other, and the slaves would fire without issues. This is properly documented on page 60 of the manual, if you don't exceed the limit of 16 units in total (slaves+masters).

Canon's radio system works great and it is super dependable. In my experience, it works 1000 better than pocketwizard, which was my previous solution. And the fact that the Master lets you know that all the slaves are ready is awesome.

I think neuro means that there can only be one master per shot -- the multiple masters function was exactly the kind you described. There is also the function where the slave can trigger the camera attached to the master, therefore acting as a kind of a master as well.

I recently got the ST E3 RT and a 600EX RT. I also had two 580EX II's. I had to sell the two 580's, as it was just a much superior system to have the 600's. It works beautifully.

I had Elinchrom triggers previously -- it worked, but it was much harder. It's kinda like when Tivo came out -- people who hadn't experienced it didn't quite get it. They asked, "doesn't a VCR do the same thing?"

Well, not really. The ease of use is the game changer. Same thing here.

Alex, if you want to trigger the 600EX with the ST-E3 and then have your manual slave triggered optically by the 600EX, there is a way to do it:

Sell your 580EX for ~$350 and buy five Yongnuo YN-560 II flashes. They are manual only -- when you set them to S2 mode they will ignore the 600EX's TTL preflash and fire during the main flash. Exactly what you want, and you can get five of them for selling just the 580EX!

I'm planning to do the following: Use three Yongnuo YN-622C wireless controllers. One on the camera, one on my 600EX-RT, and one on my 580EX-II. The YN-622C should support both flashes in E-TTL mode.

Yes, but only when using the optical-pulse set of facilities on an RT-capable body like the 5DIII. The 622C does not talk Canon RT.

I don't understand what you mean by optical-pulse set of facilities. If you have three 622 you wouldn't use Canon's RT at all, you'd just use the Yongnuo.

And just as a point, I did a 5 flash setup the otherday, but only have four 622s, so I put one 622 on my camera as a master for the other 3, and then put a 602 transmitter on top of that to trigger two 602 receivers. Bam! Dual masters!

I don't understand what you mean by optical-pulse set of facilities. If you have three 622 you wouldn't use Canon's RT at all, you'd just use the Yongnuo.

Exactly my point. The 622's will control the 600EX and the 580EX, no need to use Canon's RT at all. Love the 622s, they're cheap, feature-rich, and work very well. Saves me from having to sell the 580EX-II and buy another 600EX-RT.